fix(editor): tables with whole-number sizes, or none, show

The editor casts a table's sizes (its column width, row height, height,
and each cell's width and height) to decimals, and finds a row's default
height with a null check. JSON written elsewhere may hold whole numbers,
40 where the editor writes 40.0, or no sizes at all: such a table showed
Flutter's error box instead. The Writing System paths in an archive
brought over from elsewhere hold whole numbers. Opening content now gives
its tables their sizes as the editor reads them.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MMm7usAo6q9ZZRoPkWjoxi
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

halkyon_learn_flutter/test/core/editor/rich_content_view_test.dart

@@ -37,6 +37,61 @@ void main() {
     await tester.pump(const Duration(seconds: 1));
   }
 
+  testWidgets('shows a table whose sizes are whole numbers, or missing, as '
+      'JSON written elsewhere may hold them', (tester) async {
+    Map<String, Object?> cell(int column, int row, Map<String, Object?> data) =>
+        {
+          'type': 'table/cell',
+          'data': {'colPosition': column, 'rowPosition': row, ...data},
+          'children': [
+            {
+              'type': 'paragraph',
+              'data': {
+                'delta': [
+                  {'insert': '$column$row'},
+                ],
+              },
+            },
+          ],
+        };
+    for (final (table, cells) in [
+      // As an archive from elsewhere brought it: whole numbers.
+      (
+        {
+          'colsLen': 2,
+          'rowsLen': 1,
+          'colsHeight': 82,
+          'colDefaultWidth': 160,
+          'rowDefaultHeight': 40,
+          'colMinimumWidth': 40,
+        },
+        {'width': 80, 'height': 40},
+      ),
+      // Without the editor's sizes.
+      (<String, Object?>{'colsLen': 2, 'rowsLen': 1}, <String, Object?>{}),
+    ]) {
+      await show(
+        tester,
+        RichContent({
+          'document': {
+            'type': 'page',
+            'children': [
+              {
+                'type': 'table',
+                'data': table,
+                'children': [cell(0, 0, cells), cell(1, 0, cells)],
+              },
+            ],
+          },
+        }),
+      );
+
+      expect(tester.takeException(), isNull);
+      expect(find.textContaining('00', findRichText: true), findsOneWidget);
+      expect(find.textContaining('10', findRichText: true), findsOneWidget);
+    }
+  });
+
   testWidgets('shows the content', (tester) async {
     await show(tester, paragraph('猫は動物です。'));